High-pressure polymerization of perhaloolefins



Patented Sept. 18, 1951 HIGH-PRESSURE POLYMERIZATION OF PERHALOOLEFINSWilliam T. Miller, Ithaca, N. Y., assignor to the United States ofAmerica as represented by the United States Atomic Energy Commission NoDrawing. Application February 25, 1948, Serial No. 10,912

16 Claims.

This invention relates to the production of high molecular weightpolymers of completely halogenated olefins and more. particularly to aprocess for the polymerization of olefins completely halogenated withfluorine or with fluorine and chlorine.

This application is a continuation-in-part of my copending applicationSerial Number 730,176, filed February 21, 1947.

The polymerization of completely halogenated olefins containing onlycarbon and fluorine, or only carbon, fluorine and chlorine, has beenaccomplished at pressures up to about 1,000 atmospheres. ried out in thepresence of promoters such as organic peroxides, oxygen or inorganicperoxides. In many cases one of the principal difficulties encounteredat these pressures has been the lon period of time, usually in excess ofone or two days, necessary to achieve a satisfactory conversion to highmolecular weight polymer. In an attempt to produce a commerciallysatisfactory product, efforts were made to increase the pressure inorder to decrease the requisite polymerization time to less than 24hours. However, it was found that at pressures of the order of 1,000 toabout 7,500 kilograms per square centimeter, the polymerization productobtained without a promoter in 24 hours or less was generallyunsatisfactory. Indeed, in most cases, the molecular weight of theproduct was so low that no solid was formed but instead liquid andgrease-like polymers were obtained. For example, polymerization ofhexafluorobutadiene at 65 C. for 24 hours yielded only a small amount ofgrease-like product.

Accordingly, this invention has as one of its objects the provision of arapid process for the Such polymerizations are often car- 2 less than7,500 kilograms per square centimeter are often unsatisfactory withregard to their mechanical properties. I have found that the applicationof very high pressures of the order of 10,000 to 20,000 kilograms persquare centimeter in polymerizations of completely halogenated olefinsof the type described has yielded solid products in a considerablyshorter period of time than has heretofore been possible. Indeed,exceptionally high molecular weight, resilient polymers of completelyhalogenated olefins substituted only with fluorine, or only withfluorine and chlorine, have been obtained in 24 hours or less and inmost cases within 5 to hours. These solid polymers have excellentmechanical properties which they retain up to a relatively hightemperature. on

the other hand, the polymerization of many monomers at pressures under7,500 kilograms per square centimeter for periods of time up to 24 20hours will yield products of relatively low molecular weight, asindicated by the liquid or greaselike form of the products. Inaccordance with this invention, even at the very high pressuresinvolved, it may often be desirable to add a pro- 25 moter deliberately,such as an organic peroxide,

polymerization of completely halogenated olefins containing only carbonand fluorine, or only car bon, fluorine and chlorine.

Another object of this invention is to reduce the polymerization timefor olefins of the typ described and still to produce a commerciallysatisfactory solid polymer.

Still another object of the invention is to provide a process forproducing very high molecular weight resilient polymers ofperhalogenated olefins containing only carbon and fluorine or onlycarbon, fluorine and chlorine and having a high degree of chemical andthermal stability.

Other objects will appear hereinafter.

As has already been pointed out, the polymerization products obtainedwithout a chemical promoter in less than 24 hours under pressures of inorder to improve the polymerization reaction still further. The benefitsderived from the use of a promoter, in general, are an increased rate ofreaction, an increased yield and a higher molecular weight product underproperly selected conditions of polymerization.

When, at relatively low pressures, a promoter is employed in thepolymerization of such compounds as trifluorochloroethylene orhexafluorobutadiene-l,3 it is necessary to regulate carefully thetemperature of the polymerization at a value at which the properties ofthe promoter aid the polymerization. For example, in order to obtain thebest possible results when organic peroxide promoters are used, thetemperature of polymerization should be regulated carefully to controlthe rate of decomposition of the promoter.

' As a result, the useful range of temperatures is sembling that ofrubber even when the polymer is heated almost to its decompositionpoint. This polymer or trifluorochloroethyle'ne is resistant to attackunder almost all conditions by acids, a1- kalis, reducing or oxidizingagents, halogens and so on, and in general is a remarkably inertsubstance. The high molecular weight polymers of hexafluorobutadieneprepared under pressures in excess of 10,000 kilograms per squarecentimeter also have very desirable properties, particularly withrespect to their elasticity and thermal stability. The chemicalstability of the hexafluoro butadiene polymer is not quite so high asthat of the trifiuorochloroethylene polymer since the former retains adouble bond in each polymerization unit. However, relative to mostplastics and rubber compositions the hexafluorobutadiene high molecularweight polymer is a very inert substance. It then becomes apparent that,by reason of their elasticity and their chemical and thermal stability,such polymers are widely useful in'valve seats, gaskets, diaphragms,packing materials and the like where corrosive substances are beinghandled at temperatures where ordinary polymeric materials would beunsuitable.

The examples following hereinafter are presented to illustrate themethod of the present invention and it is to 'be understood that theyare not to be construed as a limitation of the invention.

The high pressure polymerizations described hereinafter were carried outin equipment described in The Physics of High Pressures" by P. A.Bridgeman, published by the McMillan Company, New York, in 1931. Thepressure cylinder employed had a useful volume of approximately 8 tocubic centimeters and chloroprene rubber gaskets were used to seal thepistons. In cases where a solid peroxide promoter was added the pressurecylinder was rotated in a. lathe. A steel ball was usually included inthe rotated pressure cylinder to insure complete mixing. Thetemperatures of the pressure cylinders were grams per square centimeterand approximately 83% by weight of the starting material was convertedto the solid. On heating, the solid product showed signs ofdecomposition at a temperature of about 260 C. but retained arubber-like elasticity at a temperature of at least 300 C., at whichpoint the sample was quite soft.

Example 3 Hexailuorobutadiene was polymerized under a pressure or 20,000kilograms per square centimeter for 24 hours at room temperature. Thesolid polymer on heating was capable of being spread under manualpressure at about 275 C. and was quite elastic up to 300 C. at whichpoint it was not yet melted.

Example 4 Triiluorochloroethylene was polymerized at room temperaturefor 21 hours under a pressure of 16,000 kilograms per square centimeter.The solid translucent polymer obtained was heated on a hot plate. At 200C. the polymer was roughly as elastic as natural rubber and it retainedits elasticity up to about 265 C. where it still recovered fully afterdeformation although it was quite soft. At about 270 to 275 C. thepolymer was permanently deformed on stretching.

Example 5 E l t l P 'I ramp e 0 pp iressure, emp. Yield of Solid No.Mmomer Promoter cation of kgJcm C. 1 Product Pressure None 24 hours 0002.5 gms. None 23 hours... 15, 000 25 1.95 gms. N one 9 days. 15, 00022-24 6.39 gms, 0.1 g. Benzoyl Peroxide 23 hours 15,000 22 1.98 gms.None. do 20. 000 room temp. 5.22 gms. None 21 hours 16.000 room temp.100% conversion. CzF;Cl 0.1% Benzoyl Peroxide. 4.5 hours 16, 000 Do.

maintained substantially constant during those periods when pressure wasapplied.

Example 1 Fifteen cubic centimeters of hexafluorobutadiene werepolymerized for 24 hours at a temperature of C. in the presence of 0.1benzoyl peroxide by weight based on the monomer. The applied pressurewas approximately 15,000 kilo- At a pressure of 15,000 kilograms persquare centimeter at 60 C., approximate measurement of the reduction involume of the reaction mixture indicated that the greatest proportion ofthe monomer was converted in the first five hours. After that length oftime, the rate of increase in yield was relatively small.

The application of pressures lower than about 10,000 kilograms persquare centimeter results in partial conversion of the liquid monomer tothe solid polymer, the yields of the reactions increasing with time at asomewhat higher rate than at relatively low pressures of the order of1000 atmospheres and less. However, there is a marked improvement in therate of polymerization and the yields obtained at applied pressures ofabout 10,000 kilograms per square centimeter and above. The preferredoperating range is approximately 10.000 to 20,000 kilograms per squarecentimeter while especially improved results have been obtained at about15,000 to 16,000 kilograms per square centimeter.

The present invention is particularly valuable in preparing very highmolecular weight polymers of hexafiuorobutadiene.

Although it is preferred to operate in the range of about roomtemperature to 70 C., in cases where a peroxide polymerization promoteris used, it is advantageous to maintain the temperature at a point wherea useful rate of decomposition of the peroxide takes place. Although theembodiments have been described with reference totrifluorochloroethylene and hexafiuorobutadiene it will be understoodthat the method is also applicable to other members of the class ofolefins completely halogenated with only fluorine or with only fluorineand chlorine, for example, asymmetrical difiuorodichloroethylene andcompletely substituted fiuorochlorobutadienes, and to mixtures ofmembers of this class to prepare copolymers.

Other alternatives will be apparent to those skilled in the art.

Since many embodiments might be made of the present invention and sincemany changes might be made in the embodiment described, it is to beunderstood that the foregoing description is to be interpreted asillustrative only and not in a limiting sense.

I claim:

1. A method of preparing a high molecular weight polymer of a compoundof 2 to 4 carbon atoms selected from the group consisting of olefiniccompounds of carbon and fluorine and olefinic compounds of carbon,fluorine and chlorine which comprises subjecting said compound to apressure in the range of 10,000 to 20,000 kilograms per squarecentimeter.

2. A method of preparing a high molecular weight polymer of a compoundof 2 to 4 carbon atoms selected from the group consisting of olefiniccompounds of carbon and fluorine and olefinic compounds of carbon,fluorine and chlorine which comprises subjecting said compound to apressure in the range of 10,000 to 20,000 kilograms per squarecentimeter at a temperature in the range of from room temperature to 70C.

3. A method of preparing a high molecular weight polymer of a compoundof 2 to 4 carbon atoms selected from the group consisting of olefiniccompounds of carbon and fluorine and olefinic compounds of carbon,fluorine and chlorine which comprises subjecting said compound to apressure in the range of 10,000 to 20,000 kilograms per squarecentimeter in the presence of a polymerization promoter selected fromthe group consisting of benzoyl peroxide and a borontrifluoride-dimethyl ether complex.

4. A method of preparing a high molecular weight polymer of a compoundof 2 to 4 carbon atoms selected from the group consisting of olefiniccompounds of carbon and fluorine and olefinic compounds of carbon,fluorine and chlorine which comprises subjecting said compound to apressure in the range of from 15,000 to 16,000 kilograms per squarecentimeter.

5. A method of preparing a high molecular weight polymer ofhexafiuorobutadiene which comprises subjecting the hexafiuorobutadieneto a pressure in the range of from 10,000 to 20,000 kilograms per squarecentimeter.

6. A method of preparing a high molecular weight polymer ofhexafiuorobutadiene which comprises subjecting the hexafiuorobutadieneto a pressure in the range of from 10,000 to 20,000 kilograms per squarecentimeter in the presence of a polymerization promoter selected fromthe group consisting of benzoyl peroxide and a borontrifluoride-dimethyl ether complex.

7. A method of preparing a high molecular weight polymer ofhexafiuorobutadiene which comprises subjecting the hexafiuorobutadieneto a pressure in the range of from 10,000 to 20,000 kilograms per squarecentimeter at a temperature in the range of from room temperature to C.

8. A method of preparing a high molecular weight polymer ofhexafiuorobutadiene which comprises subjecting the hexafiuorobutadieneto a pressure in the range of from 10,000 to 20,000 kilograms per squarecentimeter in the presence of benzoyl peroxide, 1

9. A method of preparing a high molecular weight polymer oftrifluorochloroethylene which comprises subjecting thetrifluorochloroethylene to a pressure in the range of from 10,000 to20,000 kilograms per square centimeter.

10. A method of preparing a high molecular weight polymer oftrifluorochloroethylene which comprises subjecting thetrifluorochloroethylene to a pressure in the range of from 10,000 to20,000 kilograms per square centimeter at a temperature in the range offrom room temperature to 70 C. in the presence of a polymerizationpromoter selected from the group consisting of benzoyl peroxide and aboron trifluoride-dlmethyl ether complex.

11. A method of preparing a high molecular weight polymer oftrifluorochloroethylene which comprises subjecting thetrifluorochloroethylene to a. pressure in the range of from 10,000 to20,000 kilograms per square centimeter in the presence of dimethylether-boron trifluoride complex.

12. A method of preparing a high molecular weight polymer oftrifluorochloroethylene which comprises subjecting thetrifluorochloroethylene to a pressure in the range of from 10,000 to20,000 kilograms per square centimeter in the presence of benzoylperoxide.

13. A method for preparing a high molecular weight polymer whichcomprises subjecting at least one compound of 2 to 4 carbon atomsselected from the group consisting of olefinic compounds consisting ofcarbon and fluorine and olefinic compounds consisting of carbon fiuorineand chlorine to a pressure of at least 10,000 kilograms per squarecentimeter.

14. A method for preparing a high molecular weight polymer whichcomprises subjecting at least one compound of 2 to 4 carbon atomsselected from the group consisting of oleflnic compounds consisting ofcarbon and fluorine and olefinic compounds consisting of carbon,fluorine and chlorine to a pressure of at least 10,000 kilograms persquare centimeter in the presence of an organic peroxide as a promoter.

15. A method for preparing a high molecular weight polymer oftrifluorochloroethylene which comprises subjectingtrifluorochloroethylene to a pressure of at least 10,000 kilograms persquare centimeter.

16. A method for preparing a high molecular weight polymer whichcomprises subjecting a conjugated perhalogenated fluorochlorobutadieneto a pressure of at least 10,000 kilo rams pe square centimeter.

. WILLIAM T. MIILER.

No references cited.

1. A METHOD OF PREPARING A HIGH MOLECULAR WEIGHT POLYMER OF A COMPOUNDOF 2 TO 4 CARBON ATOMS SELECTED FROM THE GROUP CONSISTING OF OLEFINICCOMPOUNDS OF CARBON AND FLUORINE AND OLEFINIC COMPOUNDS OF CARBON,FLUORINE AND CHLORINE WHICH COMPRISES SUBJECTING SAID COMPOUND TO APRESSURE IN THE RANGE OF 10,000 TO 20,000 KILOGRAMS PER SQUARECENTIMETER.